Past, present and future of Synthetic Aperture Radar

This tutorial is intended to briefly present the state of the art of the synthetic aperture radar (SAR). After a brief excursus on the development of the (at that time) new SAR philosophy, the tutorial continues presenting the already available operational modes of the system, from the conventional (2-D) SAR to the interferometric (3-D) IF SAR and differential DIFSAR, aimed to monitor the the surface, the topography and the changes of the observed scene, respectively. Examples of noticeble applications are presented with the aid of meaningful pictures. Unveil the future is an ill-posed problem, and statements are not granted to be accurate. Accordingly, only some open questions are considered: the tomography as an extended version of IFSAR, the full-resolution real-time on-bord processing, the forward-looking FLOSAR as appropriate modification of the side-looking SAR, and the carrierless impulse ImpSAR, the last recent accomplishment under study.